In the abrasives industry, "abrasive on a substrate" is the collective designation for numerous products consisting of a flexible substrate coated with abrasive grains. It corresponds to the designation "coated abrasives" used in most English-speaking parts of the world.
"Abrasives on a substrate" utilizing polyester yarns have been known for some time. For example, in Canadian Pat. No. 676,601, coated abrasives are described, wherein the substrate consists of a woven fabric. Such a woven fabric may consist of yarns of a varied number of polymers, including polypropylene, polyethylene and polyesters.
While the Canadian reference No. 676,601 mentions that woven substrate fabrics can be made of filament yarns, preference is given to polyester staple fibers, since fabrics of this material are better able to absorb enough abrasive grain and to provide adequate adhesion of the grain to the substrate. When using yarns of smooth continuous polyester filaments, one does indeed obtain relatively uniform substrates, but the adhesion of the grain in the substrate leaves much to be desired. Efforts have been made, therefore, to obtain a more staple fiber-like nature in filament yarns by modifying the structure thereof to obtain the advantages of continuous filament yarns in the manufacture of substrates with advantages possessed by staple fibers.
In German Pat. No. 3,218,441, various kinds of filament yarns are referred to which may serve in the manufacture of a supporting fabric used in a coated abrasives substrate. The yarns may consist of filaments having a non-circular, e.g., a triangular, cross section. Reference is also made to fibers having lateral extensions along the length of the fiber as spacing elements without explaining how those lateral extensions are to be shaped in the fiber. Reference is also made to crimped polyester filament yarns without indicating processing conditions on how to obtain the crimp for satisfactory performance as a substrate.
Furthermore, in Example 5 of this reference, it is shown in a comparison example that falsetwist textured yarns are disadvantageous for the manufacture of substrates because loops solidified with an impregnating agent protrude from the surface in a manner that abrasives manufactured with the substrate lose the binding agent grain layer after a grinding time of a few minutes.
As a consequence, until now, there has been an unfulfilled demand for a textured polyester filament yarn which can be used advantageously in the manufacture of abrasives in a substrate in such a manner that it is possible to obtain abrasives having a uniform and clean surface and a long running time; which further will not rapidly lose their binding agent grain layer during grinding; and which, beyond that, possess a high level of adhesion between substrate and abrasive grain, even in the range of fine grains; and also exhibits a substrate which exhibits a good absorbency for the binding agent used in coated abrasives.